Omni direction vehicle

ABSTRACT

An omni direction vehicle with a frame having a round surface about its perimeter with no apparatus mounted on the frame extending beyond the perimeter. Two independent drive wheels located on an axis through the center of the frame are mounted at the same distance from a central vertical axis through the frame. Each wheel is powered independently of the other and can rotate at variable speeds in either direction. The vehicle is capable of movement in any direction by rotating the axis of the drive wheels to a position which is perpendicular to the desired direction of travel. The vehicle can spin about its vertical axis such that the axis of the drive wheels can be oriented at any direction without changing the original footprint of the space that the frame occupies over the ground. Thus, the vehicle requires a zero turning radius and requires only the space it occupies to change its forward orientation.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This non-provisional application claims priority under 35 USC119(e) from Provisional Application No. 60/221,802 filed on Jul. 31,2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates generally to a wheeled vehicle designed toturn about a vertical axis. In particular, the invention relates topowered utility riding vehicles of the type useful for aircraftservicing operations, airport passenger vehicles, lawnmowers, warehouseutility vehicles, wheelchairs, or in any vehicle where rotation-in-placesteering is advantageous.

[0004] 2. Description of Prior Art

[0005] Prior art vehicles are known for turning with a zero turningradius, or so called “turning on the spot.” U.S. Pat. No. 3,938,608describes a vehicle with a single center mounted pivoting drive motorthat is rotated about a vertical axis in order to change directions ofthe vehicle. The '608 vehicle is supported with three or more swivelwheels located at equal radial distances from the center wheel. The '608outer profile is in the shape of a rectangle and has appendages thatmake close proximity maneuvering impossible next to another object suchas a post or another vehicle. Furthermore, the '608 vehicle lackstractive force because of the single drive wheel. Furthermore, a singledrive wheel must be rotated in order to change the vehicle direction,and although the single drive wheel can be turned to direct the vehiclein any direction, it does not provide directional stability for the casewhere a force is exerted on the vehicle from an angle to the line ofintended travel. For example, a force against the '608 vehicle at a 20°angle to the right or left of the line of travel would force the single'608 wheel to skid, causing loss of directional control.

[0006] The prior art concerning aircraft service vehicles has notfundamentally changed in the last fifty years. Conventional tow vehiclesfor aircraft, often called tractors, are typically configured with twoaxles, one in front, the other in the rear. The rear axle is fixed tothe vehicle and provides motive force; two additional wheels are locatedat the front end of the vehicle, each being steerable and connectedtogether to provide steering of the vehicle. Since there is a distancebetween the fixed rear drive wheels and the axis of the steerable wheelsat the front end of the vehicle, a turning radius is required that farexceeds the space actually occupied by the vehicle itself. The longerthe distance between front and rear axles, the larger the turning radiusthat is required to change directions of the vehicle. A large turningradius makes maneuvering around crowded airport ramp areas difficult andoften dangerous. Operators are required to look over their shoulders inorder to back up, and congestion is commonplace at airport and airservice facilities. All the vehicles around an airport ramp share thesecommon shortcomings. A need exists for a service vehicle that requiresless square footage for its footprints as well as the space required formaneuvering so that operator safety and the safety of the aircraft areenhanced.

[0007] Mowing vehicles share common problems with those of aircraftservice vehicles. Commercial mowers used to mow highways and large areascommonly use row-crop tractors to pull the mowers. Such tractors aredesigned to pull heavy loads such as plows in a straight line with fewturns, but mowing requires maneuvering around obstacles such as post,rails, and curbs. Furthermore, mowing must be for ravines, ditches andon hillsides. Rolling over or tipping of such equipment is a commonproblem and safety hazard. A vehicle that requires no more room than itoccupies in area for maneuvering and having a low center of gravitywould be very advantageous for all commercial mowing applications.

[0008] 3. Identification of Objects of the Invention

[0009] A primary object of this invention is to provide a servicevehicle that has enhanced maneuverability.

[0010] Another object of the invention is to provide a service vehiclethat can turn on the spot and be of the smallest physical size relativeto the space it occupies.

[0011] Another object of the invention is to provide a service vehiclewhich reduces the risk of accidents which result in damage or injury toequipment or operating personnel.

[0012] Another object of the invention is to provide a service vehiclehaving an outer perimeter that defines an outer imaginary cylinder thatencloses any equipment or appendages mounted on the vehicle therebyenhancing its capability to maneuver the vehicle without hanging up onobjects external to the vehicle.

[0013] Another object of the invention is to provide a service vehiclewith structures mounted thereon for materials handling or peopletransport.

[0014] Another object of the invention is to provide a service vehiclethat can be used for towing, pushing or handling aircraft equipment.

[0015] Another object of the invention is to provide a mowing machinethat can turn on the spot and maneuver easily about obstructions.

[0016] Another object of the invention is to provide a people-movingcart for use at an airport, where the cart can turn around on the spotand be of the smallest physical size relative to the space it occupies.

SUMMARY OF THE INVENTION

[0017] The objects identified above along with other features andadvantages of the invention are incorporated in a vehicle that, due to acombination of its characteristics including its shape and theconfiguration of its drive wheels, provides unique maneuverability andefficiency. When the vehicle is combined with a radial movable hitch toits circular frame, such combination provides for free circumferentialattachment to and movement of other vehicles for transport of suchvehicles with minimal space required for maneuverability and safety ofoperation. Such vehicles include aircraft baggage loading equipment,baggage carts, tractors and other wheeled equipment adapted for aircraftand airport operations.

[0018] The vehicle according to the invention has a frame with aperfectly round outer surface about its perimeter with no externalappendages. That outer surface is characterized as a perfect,unobstructed smooth circle defined by a vertical axis of the vehicle.The vehicle has two independent drive wheels located on a horizontalaxis which intersects the vertical axis. Each wheel is at exactly thesame distance from the vertical axis, with each wheel having thecapability to move independently and at infinitely variable speeds ineither direction. Thus, the vehicle is capable to move in any directionby rotating the axis of the drive wheels perpendicular to the desireddirection of travel. By applying motive force to the wheels in theappropriate direction and speed, the vehicle can turn and move in anydirection perpendicular to the axis of the drive wheels within the areacovered by its circumference. Rotating about the vertical axis to anyradial position without changing its original footprint, the vehiclerequires a true zero turning or maneuvering radius, and thus requiresonly the space that it occupies in which to maneuver in any direction.The “footprint” is the area on the ground below the vehicle when it isat rest.

[0019] The capability to maneuver with a zero turning radius in additionto having a perfectly round and smooth perimeter with no apparatus whichis mounted on the frame of the vehicle which extends beyond the outerperimeter of the frame provides for virtually unlimited directionalmovement and requires no maneuvering space beyond the area or footprintcovered by the vehicle itself. The space required of the vehicle is nogreater than that of a conventional vehicle with a drive axle and asteering axle.

[0020] One embodiment of the invention is in a vehicle capable ofpulling single or multiple pieces of equipment such as trailers orvarious sized objects such as aircraft. In this configuration as a towvehicle or tractor, the vehicle is equipped with a smooth outer ringincluding upper and lower rails which support a trolley. The trolleyincludes a plurality of precision wheels or rollers that are rotatablycoupled to the upper and lower rails of the outer ring and enable thetrolley to move freely around the entire circumference of the outer rimof the vehicle. The trolley can be rotated either manually, or throughthe use of a motor, for positioning the trolley to the desired positionat any point about the circumference of the vehicle prior to connectionto the object to be moved. Attached to the trolley or “truck assembly,”via a hitch is a pivoting arm that can be stored in the verticalposition perpendicular to the ground, or when in use, lowered to aposition approximately parallel to the ground where it may then beattached to either a towable trailer or another object to be moved suchas an airplane. The connecting arm is capable of movement about an arcvertically from its pivot point, but not laterally relative to the pivotpoint.

[0021] When the connecting arm is then connected to the object to bemoved, and after the axis of the tow vehicle drive wheels is positioned(by operator action) perpendicular to the desired direction of movement,the tow vehicle exerts a pushing or pulling motive force against theobject (e.g., trailer or airplane) being towed or pushed. The directionof travel of the towed or pushed object can be changed by adjusting theangle of the connecting arm or hitch relative to the direction of travelof the axis of the tow vehicle drive wheels. This is accomplished byrotating the axis of the drive wheels of the tow vehicle radially to anydesired angle relative to the object being towed or pulled and thenexerting forward or reverse power to the drive wheels. Because thetrolley assembly to which the connecting arm is attached is capable ofmovement freely about the circumference of the tow vehicle, the angle ofthe connecting arm or hitch can constantly be adjusted to achieve thedesired direction of travel of the object being pulled or pushed. Thischanging of relative angle and direction does not transmit any stress tothe object being pushed or pulled, because the speeds of the drivewheels are continuously variable from zero to maximum and the trolleyand arm move about the circumference of the tow vehicle with very littleif any friction.

[0022] The arrangement of a substantially outer circular shape of avehicle with a smooth and unobstructed outer perimeter in combinationwith two, independently variable speed bi-directional drive wheelslocated on a single axis through the exact center of the vehicle andmobile connecting point or hitch that is free to move about the fullcircumference of the vehicle working in conjunction with aperpendicularly fixed connecting bar results in a tow vehiclecharacterized by the ability to move omni-directionally about a givenpoint, change directions with zero maneuvering room beyond the physicalfootprint of the vehicle, and push or pull other mobile vehicles withprecise control. Such characteristics reduces the operating space on theground required to move or handle an object being manipulated thusincreasing operating efficiency. Safety is increased because theoperator of such a vehicle, positioned directly at the center of the towvehicle, can always be facing the direction the vehicle is moving, neverhaving to back up and look backward.

[0023] Whether pushing or pulling another object such as an aircraft ortrailer or cart, the field of vision of the operator of the tow vehicleis always facing the direction of movement of the vehicle. In operation,the operator rotates the axis of the drive wheels until it isperpendicular to the direction of the desired travel by rotating onewheel in one direction and the other in the opposite direction. Once thedesired drive axle orientation is reached (perpendicular to the desireddirection of travel), both wheels are given power equally, causing thevehicle to move in the direction perpendicular to the drive wheel axisof the tow vehicle axle. The vehicle being towed or pushed is thensteered in the new direction and the angular attitude between the towvehicle and the steering axle of the vehicle being towed or pushedautomatically comes into an appropriate geometry as the radial hitchtravels about the perimeter of the tow vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention is described below with reference to preferredembodiments which are illustrated by drawings of which:

[0025]FIGS. 1A and 1B are top and side views of the Omni DirectionVehicle (ODV) according to the invention schematically showing majordrive components, a circular rail about the frame of the ODV, and atrolley rotatably mounted on the rail;

[0026]FIGS. 2A and 2B are side and top views of a hitch mounted on thetrolley with a more detailed illustration of rotatable mounting of thetrolley on the circular rail of the ODV;

[0027]FIGS. 3A and 3B are illustrations of the ODV pushing an airplanesuch that airplane is caused to turn while being pushed;

[0028]FIG. 4 illustrates an ODV pulling trailers which are configured inthe same manner as the ODV but without drive power capability to theirwheels;

[0029]FIGS. 5A and 5B illustrate, with top and side views, an ODVaccording to the invention configured as a baggage vehicle fortransporting and loading baggage to and from the baggage compartment ofan airplane as illustrated by FIG. 6;

[0030]FIGS. 7A and 7B are top and side views of an ODV according to theinvention configured as a hydrant vehicle for fueling an aircraft;

[0031]FIGS. 8A and 8B are top and side views of an ODV according to theinvention configured as a sanitary service tank truck for servicing anaircraft;

[0032]FIG. 9 is a top view of an ODV without a trolley according to theinvention configured as a mowing machine; and

[0033]FIGS. 10A and 10B are top and side views of an ODV according tothe invention configured as a passenger cart for airport operations totransport passengers between locations in an airport.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0034]FIGS. 1A and 1B illustrate an Omni Directional Vehicle (hereafterODV) according to the invention which includes primary wheels 2 mountedon a frame 1 which has an outer perimeter in the shape of a circle. Thecircular frame has a vertical axis 110, illustrated in FIG. 1B and whichis perpendicular to the plane of the top view of FIG. 1A. The wheels 2(powered in the powered version of FIGS. 1A, 1B, 3A, 3B, etc., butunpowered in the trailer version of FIG. 4) are mounted along ahorizontal axis 120 which is perpendicular to the vertical axis 110 andintersects the vertical axis 110 as shown in FIGS. 1A and 1B. Two swivelcastor wheels are pivotably mounted to the frame at the rear of the ODV100.

[0035] In the powered version of the ODV 100, a power source 4 mountedon the frame 1 is provided for driving hydraulic pumps 5. The powersource 4 may be a diesel or gasoline engine or an electric motor/batteryassembly. The pump 5 provides balanced pressurized hydraulic fluid toseparate hydraulic motor 6 gearbox assemblies, one for each wheel 2. Thespeed and direction of rotation of motors 5 and wheels 2 is controlledby control levers 7 which operate hydraulic control valves (notillustrated) coupled to hydraulic motors 6. The control levers 7 andvalves operate exactly the same for each of the left and right wheels 2.Each lever 7 and valve has a neutral position, such that when a lever isat such neutral position, a wheel associated with that lever ishydraulically braked. If a lever is moved forward, the wheel motor 6begins to move slowly forward for turning a respective wheel 2. Thegreater distance that a lever 7 is pushed or pulled from its neutralposition, the faster the wheel motor 6 turns, thereby causing the wheel2 to which it is coupled to increase in speed. A seat 13 for theoperator is mounted on frame 1 with the vertical axis 110 passingthrough it.

[0036] If both levers 7 are moved in the same direction and amount andat the same time, both drive wheels 2 move at the same speed, therebycausing straight-ahead movement of the ODV over the ground. Thatmovement is perpendicular to the horizontal axis 120. If the levers 7are pushed forward or backward at an unequal distance from each other, alever moved the greatest distance will produce a greater speed ofrotation than the other one, causing the vehicle to turn with thevehicle turning about the wheel that is turning slower. For example, ifthe right control lever 7 is pushed farther forward than is the leftlever 7, the ODV 100 turns to the left, and vice versa.

[0037] If the right lever 7 is moved forward and the left lever 7 ismoved backward, and both lever positions are the same in amount andopposite in direction, the left wheel turns backward, the right wheelturns forward both at the same rate of rotation and the ODV 100 turns inits own space or footprint without moving from that footprint while itis turning. The footprint over the ground is the area of the groundbeneath the circular frame 1. The counter clockwise rotation describedabove, becomes a clockwise rotation when the right wheel 2 rotatesbackward at the same rate as the forward rotation of the left wheel 2.Thus, the ODV 100 in its basic form can change its heading while notvarying its footprint over the ground during such a change of heading.That means that if the ODV does not interfere with any object on theground, with one heading, that heading can be changed without fear ofinterfering with any object on the ground, because the ODV footprintdoes not change during heading correction.

[0038] The two wheels 2 (or main wheels of the trailer of FIG. 4) arelocated in the exact center axis of the vehicle. Two additional swivelwheels or castors 3 (as best illustrated in FIGS. 1A, 1B) are mounted atthe rear of the vehicle. The castors 3 provide support for balancing theweight of the vehicle, because the power source 4 and other ballastweight (if desired) is used to counterbalance the ODV 100 and keep theframe 1 substantially level. The rear swivel castors 3 support thiscounterbalanced weight. The swivel castors 3 are mounted on the frame 1at positions so as not to protrude from the outer circumference of thevehicle when the vehicle is turning about itself (i.e., spinning) aboutvertical axis 110 in order to assure that there are no externalappendages on the vehicles that could touch or catch other objects whilethe ODV 100 is spinning about axis 110. When the ODV 100 moves forward,the castors trail outside the outer circumference of the ODV frame 1without any substantial effect on the obstruction free characteristicsof the vehicle. One or more swivel castors 3 may be employed dependingon weight and application of vehicle 100.

[0039] The hitch rail 8 is mounted to the frame 1, for example via aplurality of mounting plates or stanchions 26 (see FIGS. 2A, 2B). Thehitch rail 8 provides a smooth running surface for at least one hitchtrolley assembly 9. Where the ODV is arranged and designed as airportservice operations, for example, two or more trolley assembly may bedesigned for different hitch arrangements, one for pushing an aircraftto or away from the terminal, another for service trailers, and so on.The hitch assemblies may be manually rotated about rail 8 or they may berotated by powered assemblies with electric or hydraulic motors forexample. Plural trolleys 9 (only one of which is illustrated in FIGS.1A, 1B) may be coupled together so that they move in tandem orseparately depending on the application.

[0040]FIG. 2A illustrates a side view of the hitch rail 8 and itsattachment to the main frame 1 with stanchions 26 spaced around thecircumference of the vehicle. Trolley cams 27 located on the side of therail 8 on the top and the bottom of the rail 8 support the trolley 9 andprovide a mounting platform for various hitches and connections to theODV 100. The cams are positioned preferably with one upper and lower camset 27 outboard of the rail 8, and with two upper and lower cam sets 27inboard of the rail 8. The mounting positions of the outboard cams andthe inboard cams are with respect to the trolley 9 so that the radius ofcurvature from inboard cam set 27 to the outboard cam set 27 issubstantially the same as the radius of curvature of the rail 8, thusallowing the trolley to rotate smoothly with minimum friction andresistance about rail 8. This freedom of movement reduces stress on thevehicles being moved, such as aircraft that typically have delicatelanding gear. FIG. 2B illustrates the trolley 9 from a top view. The twocams 27 located inboard of the rail 8 and one cam 27 located outboard ofthe rail 8 trap the rail 8 with substantially no looseness.

[0041]FIG. 3A illustrates the ODV 100 pushing an airplane 150 byrotating wheels 2 of the ODV 100 such that the forward direction of theODV 100 as depicted by the arrow F. The forward direction isperpendicular to the horizontal axis running through the wheels 2. Thearrow F is directed to the left of the centerline of the airplane andwith both wheels moving forward at the same rate, the nosewheel of theairplane is turned to the left, causing the airplane to move in acounter clockwise arc as it is pushed rearward. FIG. 3B shows theopposite maneuver, when the ODV 100 is rotated to the right in the sanemanner, causing the opposite movement of the nosewheel and a clockwiserotation of the airplane 150 as it is pushed rearward. In this manner,the ODV 100 is capable of controlling the direction of movement of theairplane in a smooth, uninterrupted manner. Because the controls 7 ofthe drive wheels 2 of the ODV 100 are continuously variable, and verysmooth, it is possible to move at only creeping speeds up throughmaximum travel speeds without changes in gears or interrupting themovement of the airplane 150 or other object being pushed.

[0042]FIG. 4 illustrates a powered ODV 100 pulling a series of trailers29 each configured with the same round shape and hitch trolley as theODV tractor 100. The main wheels 2A are located on the center axis 120Aof the perfectly round trailers and have castors like the ODV. Thehitches 9 working in concert with the tractor 100 enable the train oftrailers to move in very close proximity and use very little maneuveringroom.

[0043] The description of the ODV 100 above shows its usefulness as apushing or pulling vehicle for airport operation. The ODV of theinvention described above can also serve as the basis for other servicevehicles.

[0044]FIGS. 5A and 5B illustrate a baggage loading/unloading vehicle 200which utilizes a similar frame and undercarriage as illustrated in FIGS.1A and 1B but a trolley hitch is not necessarily required. The uppersurface of the vehicle 200 supports an annular carousel or conveyor 11that is used to support baggage and other freight as it is beingunloaded off an airplane. The operator sits in the center of thecarousel 11 for moving the vehicle 200 from the aircraft to a baggageroom, etc. When the carousel 11 of the vehicle 200 reaches the side ofthe aircraft, it is hydraulically elevated by hydraulic pistons 12 (asillustrated in FIG. 6) to accept baggage from the floor of the aircraft15 and transport the baggage to ground level where it may be loaded ontowaiting trailers or carts for transport. Because the carousel 11 is ofan annular shape and without end, freight handlers are able to continueloading its flat surface as it rotates until it is full. Unlike straightconveyor belts that become full and dump freight off the end onto theground, the ODV carousel accepts baggage until there is no further room,but when full, the rotating movement of the carousel does not dump thebaggage to the ground. The arrangement of FIG. 6 can be built on anyscale with segmented and hinged carousel surfaces for transport asrequired for larger aircraft.

[0045]FIGS. 7A and 7B illustrate the ODV principle as described above ina vehicle outfitted as a hydrant refueler 300. In this arrangement, thesame undercarriage is used as the ODV tow vehicle of FIGS. 1A, 1B;however, on the top of the chassis or frame 1, several elements aremounted: one or more hose reels 17 with single point nozzles 18, afilter separator 16, a meter 20 and a hydrant connection 19 with anarticulated hard pipe arm 21 that allows for connection to undergroundhydrant fuel systems. Maneuvering of hydrant refuelers around crowdedairport ramps under the wings of commercial aircraft can be difficultand dangerous due to the flammable nature of fuel. The ODV hydrantrefueler of FIGS. 7A, 7B enables safer maneuvering without maneuveringspace other than that that the vehicle occupies.

[0046]FIGS. 8A and 8B illustrate the ODV principle as described aboveconfigured as a tank vehicle 400 that is used to service the sanitarydischarge of commercial aircraft, or to deliver fresh potable waterduring servicing at the gates between flights. The entire chassis 23 isconstructed as a cylindrical tank for holding liquid. The outside of thetank is round and to be dimensioned to be within the circular radius ofthe frame of the vehicle. Appropriate drive wheel capacity and hose 24connections are provided with hydraulically driven pumps (not shown) tomove the various liquids. The maneuverability of the vehicle 400 makesit easier to navigate crowded ramp areas of airports.

[0047]FIG. 9 illustrates a mowing tractor 500 based upon the ODVprinciple described above. A plurality of appropriately sized and spacedrotor cutting blades 22 provide for a full cutting swath equal to themaximum diameter of the vehicle. The unique maneuvering capabilities ofthe ODV make mowing around signs, posts, railing, curbs and otherobstacles much more efficient. Because the vehicle has an extremely lowcenter of gravity, rollover is virtually eliminated. Accessory itemssuch as full gimbal mounting of the driver's seat make hillsideoperation safe. The main chassis can be segmented from front to rearmaking navigation of uneven surfaces possible. Such uneven surfacesinclude sides of ditches or ravines.

[0048]FIGS. 10A and 10B illustrate a passenger cart 600 for air terminalpassenger transport based upon the ODV principle discussed above. Anannular shaped bench 80 is secured to the frame of the vehicle. Theoperators seat 8 and control levers 7 are mounted higher on the vehicleto enable the operator to view the airport terminal over the passengerseated on the bench 80. In operation, the operator loads passengers forseating on the bench 80. Preferably the passenger seat faces outwardlyfrom the center of the vehicle. When the operator must turn the cart 600around, the vehicle turns on the spot and after turning 180°, forexample, is capable of turning around with zero turning radius.

[0049] As described above, an ODV vehicle of the invention ischaracterized by a perfectly round outer perimeter with no appendagesextending radially from that outer perimeter that can hang up or catchon objects or equipment on the ground. The ODV arrangement with drive ormain wheels positioned along a horizontal axis that runs through thecenter of the circular frame, and where both wheels functionindependently of each other in forward and rearward directions providesa basis for many service vehicles, some of which are described above.

[0050] The invention as described above is defined by the claims whichfollow.

What is claimed is:
 1. A powered vehicle comprising, a frame having a shape of a circular disk with a vertical axis defined at the center of said circle disk, said frame characterized by an outer radius as measured from said vertical axis, first and second drive wheels coupled to said frame, each of said drive wheels capable of powered rotation about a horizontal axis that intersects said vertical axis, each of said drive wheels capable of forward and rearward rotation about said horizontal axis, at least one castor mounted to said frame for supporting said frame on the ground by at least said first and second drive wheels and said castor, said vehicle having no equipment mounted on said frame which extends beyond the radius of said circular disk when said vehicle spins about said vertical axis, means for independently controlling the direction of rotation and the speed of said first and second drive wheels, whereby when said first and second drive wheels are rotated in opposite directions and at substantially the same speed, said vehicle spins about said vertical axis and no equipment of said vehicle extends outwardly from said vertical axis beyond said outer radius.
 2. The vehicle of claim 1 further comprising a hitch rotatably coupled about the outer perimeter of said frame, said hitch being arranged and designed to couple to a bar which is arranged and designed for connection to a device to be pushed or pulled.
 3. The vehicle of claim 1 wherein said frame includes a circular rail disposed about the outer perimeter of said frame and said vehicle further comprises a trolley rotatably supported on said rail, and said trolley including a hitch for coupling to a first end of a bar which is arranged and designed to be connected at a second end of the bar to a device to be pushed or pulled.
 4. The vehicle of claim 1 wherein two castors are mounted to said frame for supporting said frame on the ground by said first and second drive wheels and said two castors, each of said castors being mounted at a position on said frame so that when said vehicle spins about said vertical axis, wheels of said castors turn to be within said outer radius.
 5. The powered vehicle of claim 1 further comprising an operator seat mounted on said frame at a position intersected by said vertical axis and between said first and second drive wheels.
 6. The powered vehicle of claim 5 further comprising a first control lever positioned on a first side of said operator seat, said first control lever operatively coupled to a first power source for controlling the speed and direction of rotation of a first drive wheel, and a second control lever positioned on a second side of said operator seat, said second control lever operatively coupled to a second power source for controlling the speed and direction of rotation of a second drive wheel, wherein each of said first and second drive wheels are controlled independently of each other.
 7. The powered vehicle of claim 3 wherein said first end of said bar is coupled to said hitch, and wherein said second end of said bar is connected to wheels of an aircraft and said powered vehicle is capable of pushing or pulling an airplane.
 8. A tow tractor and trailer combination comprising a tow tractor having a tractor frame with an outer tractor rail which is in the shape of a circle defined about a vertical axis through said tractor frame, said tractor having no apparatus mounted on the top side of said tractor frame which extends beyond the circular radius of said outer tractor rail, first and second drive wheels coupled to said frame, each of said drive wheels capable of powered rotation about a horizontal axis that intersects said vertical axis, each of said drive wheels capable of forward and rearward rotation about said horizontal axis, at least one castor mounted to said frame for supporting said frame on the ground by at least said first and second drive wheels and said castor, a tractor trolley rotatably supported on said tractor rail and including a tractor hitch for coupling to a first pull bar, said tow tractor having a power source mounted on said tractor frame and being arranged and designed when powered by said power source to spin about said vertical axis with no apparatus mounted on said tractor frame extending outwardly beyond said circular radius, and a trailer having a trailer frame with an outer trailer rail which is in the shape of a circle defined about a vertical axis through said trailer frame, first and second main trailer wheels coupled to said trailer frame, each of said main trailer wheels mounted for rotation about a horizontal axis that intersects said vertical axis through said trailer frame, at least one castor mounted to said trailer frame for supporting said frame on the ground by at least said first and second main wheels of said trailer and said castor, a trailer trolley rotatably supported on said trailer rail and including a trailer hitch for coupling to a second pull bar, said first pull bar being connected between said tractor hitch and said trailer frame.
 9. An aircraft service vehicle comprising a frame supported on the ground by wheels and with an outer rail which is in the shape of a circle defined by a radius about a vertical axis through said frame, said frame having no apparatus mounted thereon which extends beyond the radius of said circle of said outer rail, said vehicle having a power source mounted on said frame with operation controls and being arranged and designed when powered by said power source to turn about said vertical axis with no apparatus mounted on said frame extending outwardly beyond said circular radius.
 10. The vehicle of claim 9 further comprising an operators seat mounted on said frame and intersecting said vertical axis through said frame with drive wheels mounted on said frame along a horizontal axis which intersects said vertical axis, said drive wheels coupled to said power source and arranged and designed to rotate independently in forward and backward directions.
 11. The aircraft service vehicle of claim 10 further comprising, an endless conveyor belt mounted on said frame, said conveyor belt being annular in shape and having an annular width which extends from an inner radius of an inner circle about said operators seat and defined about said vertical axis and an outer circle.
 12. The aircraft service vehicle of claim 11 further comprising, means for raising an end of said conveyor belt for vertical alignment with an aircraft baggage door in an upper position or lowering same for vehicle translation.
 13. The aircraft service vehicle of claim 10 further comprising, aircraft fueling apparatus mounted on said frame.
 14. The aircraft service vehicle of claim 10 further comprising, at least one tank mounted on said frame for holding liquids and a hose in fluid connection with said tank for servicing an aircraft.
 15. The vehicle of claim 10 wherein, said at least one tank is arranged and designed for supplying potable water for onloading to an aircraft.
 16. The vehicle of claim 15 wherein, said at least one tank is arranged and designed to carry wastewater for offloading from an aircraft.
 17. The aircraft service vehicle of claim 9 further comprising means carried by said frame for supporting passengers, and an operators seat mounted on said frame and intersecting said vertical axis through said frame with drive wheels mounted on said frame along a horizontal axis which intersects said vertical axis, said drive wheels coupled to said power source and arranged and designed to rotate independently in forward and backward directions, whereby airport passenger transport operations are enhanced by requiring zero turning radius.
 18. The vehicle of claim 17 wherein said means carried by said frame is a circular bench, and said operators seat is elevated to a position enabling an operator to see above passengers seated on said bench.
 19. A mowing machine comprising a frame supported on the ground by wheels and with an outer rail which is in the shape of a circle defined about a vertical axis through said frame, said frame having no apparatus mounted thereon which extends beyond the circular radius of said outer rail when said frame turns about said vertical axis, said vehicle having a power source mounted on said frame with operation controls and being arranged and designed when powered by said power source to turn about said vertical axis with no apparatus mounted on said frame extending outwardly beyond said circular radius, an operators seat mounted on said frame and intersecting said vertical axis through said frame with drive wheels mounted on said frame along a horizontal axis which intersects said vertical axis, said drive wheels coupled to said power source and arranged and designed to rotate independently in forward and backward directions, and a plurality of cutting blade assemblies mounted on said frame, each assembly powered by said power source, said assemblies mounted inside said circle so that no part of any cutting blade extends beyond said circle.
 20. The mowing machine of claim 19, wherein said cutting blade assemblies are mounted along an arc inside said circle and are arranged and positioned on said frame to provide cutting coverage along substantially the entire diameter of said frame. 